Getting your 1350 u joint measurements right is the difference between a smooth ride and a vibrating mess that eats your transmission seals. If you're working on a heavy-duty truck, a beefy muscle car, or some kind of off-road beast, you've probably realized that not all universal joints are created equal. The 1350 series is a staple in the performance world, but if you guess the size instead of measuring, you're going to have a bad time when you try to press those caps in.
It's one of those things that seems simple until you're lying on a cold garage floor with a set of calipers, wondering if that 0.002-inch difference actually matters. Spoiler alert: it does. Let's break down how to actually measure these things so you don't end up returning parts three times.
Why the 1350 Even Matters
Before we dig into the numbers, it's worth noting why everyone talks about the 1350. It's basically the "gold standard" for high-strength applications. While the smaller 1310 series is fine for your average daily driver, the 1350 is built to handle way more torque. It's got a thicker cross and larger bearing caps, which means more surface area to distribute the load.
If you're pushing 500 horsepower or you've got a heavy 4x4 with 35-inch tires, you're likely looking for 1350 u joint measurements because your stock setup just isn't cutting it. It's the go-to for 1-ton trucks and serious drag racers for a reason.
The Two Big Numbers You Need
When you're looking at 1350 u joint measurements, you really only care about two specific dimensions. If you get these two right, the joint will fit. If one of them is off, it won't.
1. The Cap Diameter
First up is the diameter of the bearing cap. For a standard 1350 series u-joint, the cap diameter is 1.188 inches.
In the shop, most guys just call this "one and three-sixteenths." If you're using a digital caliper—which you absolutely should be—you're looking for that 1.188 reading. If you see 1.063, you're looking at a 1310 or 1330. That small difference is enough to make the joint either fall right through the yoke or not even start to fit.
2. The Overall Width
The second number is the width of the u-joint with the caps installed and compressed. For a 1350, that width is 3.625 inches.
This is often referred to as "three and five-eighths." You measure this from the outer face of one cap to the outer face of the opposite cap. This measurement ensures the joint will sit properly between the "ears" of your yoke or inside the driveshaft flanges.
Using the Right Tools for the Job
I can't stress this enough: put the tape measure back in the junk drawer. A tape measure is great for framing a wall, but it sucks for 1350 u joint measurements. You need a pair of calipers.
Digital calipers are cheap these days, and they'll save you hours of frustration. When you're measuring the yoke, you're looking for the distance between the tabs that hold the caps in place. If that distance is 3.625 inches and the hole for the cap is 1.188 inches, you've got a 1350 setup.
If you try to "eyeball" it, you'll likely confuse the 1350 with the 1330. Why? Because the 1330 also has an overall width of 3.625 inches. However, the 1330 uses a smaller cap (1.063 inches). If you only measure the width and skip the cap diameter, you'll buy the wrong part every single time.
Snap Rings: The Hidden Detail
Another part of the 1350 u joint measurements conversation is how the joint is actually held in place. The 1350 series almost exclusively uses external snap rings. These are the little C-clips that fit into a groove on the yoke, sitting just outside the cap.
Some other series, especially those found in OEM Chevy or Dodge applications (like the S44 or 3R series), use internal clips that sit on the inside of the yoke ears. If you see grooves on the inside of your yoke rather than the outside, you might not be looking at a standard 1350, even if the width seems close.
Always check where those clips live. For a true 1350, you're looking for that external snap ring setup. It's the strongest way to keep everything locked together when you're pinning the throttle.
Comparing 1350 to Other Common Sizes
Sometimes it helps to see the 1350 u joint measurements side-by-side with its cousins just to make sure you haven't misidentified what's in your hands.
- 1310 Series: 3.219" wide with 1.063" caps. Small, common on older Jeeps and small cars.
- 1330 Series: 3.625" wide with 1.063" caps. This is the "big brother" to the 1310, sharing the same cap size but having the width of a 1350.
- 1350 Series: 3.625" wide with 1.188" caps. The heavy hitter.
As you can see, the 1330 and 1350 share the exact same width. This is exactly where most people trip up. They measure the width, see 3-5/8", and order a 1350. Then they get it home and realize the caps are way too big to fit into their 1330 yoke. Don't be that guy. Measure the cap!
What About Conversion Joints?
Life would be easy if every part of your drivetrain matched, but we all know that's rarely the case. Maybe you swapped in a Ford 9-inch rear end that has a 1350 yoke, but your existing driveshaft is set up for 1310 joints.
This is where "hybrid" or conversion joints come in. You can actually find u-joints that use 1350 u joint measurements on one axis and 1310 measurements on the other. This allows you to mate two different series together without having to build a whole new driveshaft.
If you're doing this, you need to be twice as careful with your measurements. You'll need to measure the width and cap diameter for the driveshaft side, and then do the same for the yoke side. It's a bit of a jigsaw puzzle, but it's a lifesaver for custom builds.
Identifying Wear Before You Measure
If you're pulling an old joint out to get your 1350 u joint measurements, take a look at the condition of the yoke ears. If a u-joint has failed violently, it can actually stretch the yoke.
If you measure the yoke and find that it's 3.640 inches instead of 3.625, your yoke is likely "sprung." Putting a brand new 1350 joint into a stretched yoke is a recipe for disaster. The joint won't sit centered, which causes a nasty vibration that will eventually destroy your pinion bearings.
The same goes for the cap holes. If the old cap was spinning inside the yoke, the hole might be egg-shaped. If your calipers show the hole is wider in one direction than the other, it's time to toss that yoke and get a new one. Precision matters here—we're talking about a heavy metal shaft spinning at thousands of RPMs right under your seat.
Greaseable vs. Non-Greaseable Joints
Once you've confirmed your 1350 u joint measurements, you usually have to choose between a greaseable joint (with a zerk fitting) and a solid (non-greaseable) joint.
- Solid joints are generally considered stronger because the cross isn't hollowed out for grease channels. Most drag racers and high-horsepower guys prefer these.
- Greaseable joints are great for daily drivers or mud trucks where you want to flush out contaminants.
Regardless of which one you pick, the external dimensions will stay the same. A greaseable 1350 will still have that 1.188-inch cap and 3.625-inch width.
Final Thoughts on Precision
It might seem like overkill to worry about a few thousandths of an inch, but in the world of drivelines, that's a huge margin. Getting your 1350 u joint measurements spot on ensures that your car or truck stays reliable.
Take your time, use a decent set of calipers, and double-check both the width and the cap diameter. If you do that, you'll spend more time driving and less time under the truck cursing at a part that doesn't fit. Whether you're upgrading for more power or just doing some routine maintenance, knowing exactly what you're working with makes the whole process a lot smoother.